In the present cellular systems such as long-term evolution (LTE) systems, when an inactive mobile (radio resource control idle state (RRC_IDLE) user equipment (UE) in LTE terminology) is to be paged, a paging message is broadcast by multiple cells in a certain area called a tracking area (TA). The paging message for the idle UE is initialized by a mobility management entity (MME) of the LTE network, which is normally aware that the UE is located within the tracking area but does not know within which macro cell of the tracking area the UE is located. When the UE is not in communication with any base station because the UE is currently idle, it is not possible to locate the macro cell of the tracking area in which the UE is located.
FIG. 1 depicts the situation. In exemplary system 100 of FIG. 1, there are a plurality of macro cells (macro cell 102, macro cell 104, macro cell 106, macro cell 108, macro cell 110, macro cell 112, macro cell 114, macro cell 116, macro cell 118, macro cell 120, macro cell 122, macro cell 124, macro cell 126, macro cell 128, macro cell 130, macro cell 132, macro cell 134, macro cell 136, macro cell 138), and a plurality of corresponding macro cell base stations (macro cell BS 103, macro cell BS 105, macro cell BS 107, macro cell BS 109, macro cell BS 111, macro cell BS 113, macro cell BS 115, macro cell BS 117, macro cell BS 119, macro cell BS 121, macro cell BS 123, macro cell BS 125, macro cell BS 127, macro cell BS 129, macro cell BS 131, macro cell BS 133, macro cell BS 135, macro cell BS 137, macro cell BS 139). The macro base stations are sometimes referred to as eNodeB devices. In system 100 there are also a plurality of mobility management entities (MME 1 161, MME 2 163, MME 3 165). MME 1 161 corresponds to tracking area A 160 which includes macro cells (102, 104, 106, 108, 110, 112); MME 2 163 corresponds to tracking area B 162 which includes macro cells (114, 116, 118, 120, 122, 124); and MME 3 165 corresponds to tracking area C 164 which includes macro cells (126, 128, 130, 132, 134, 136, 138).
Macro cell 132 further includes femto cell base station 141 with corresponding femto cell 140. Exemplary UE device 150 is situated in macro cell 132. Consider the case where UE device 150 is in an idle state of operation, e.g., UE is in RCC_IDLE state.
When the idle UE 150 in tracking area C 164 needs to be paged, the corresponding MME (MME 3 165) normally forwards the page to all the macro base stations, e.g., eNBs, and all the small cell base stations, e.g., femto base stations, in the tracking area C 164. The page is then broadcast by the macro base stations and femto base stations. Thus MME 3 170 sends, e.g., via a backhaul coupling MME 3 165 to the base stations, page signal 170, for paging idle UE 150, to macro base stations (127, 129, 131, 133, 135, 137, 139) and femto base station 141. The base stations (127, 129, 131, 133, 135, 137, 139, 141) generate and transmit page signals (171, 172, 173, 174, 175, 176, 177, 178), respectively, in response to received signal 170 from MME 3 165.
While page signals (174, 178) within cell 132 may be useful, the pages (171, 172, 173, 175, 176, 177) in the cells (126, 128, 130, 134, 136, 138) can be wasteful since the UE 150 is within the coverage area of cell 132 and is camping on the base station 133 and may be out of communication range of the base stations (127, 129, 131, 135, 137, 139) of other cells (126, 128, 130, 134, 136, 138) of tracking area C 164. Thus wireless paging signals (171, 172, 173, 175, 176, 177) may be unnecessary, can waste power and/or air link resources, and/or may generate unnecessary interference.
Based on the above discussion, it would be beneficial if new methods and apparatus were developed which facilitated more efficient paging for idle state UEs, e.g., methods and apparatus which identified a smaller paging area corresponding to an idle state UE.